{abundance}
{sylvan library}
If I replace all of my card draws with Abundance's "reveal until... and put in hand", I won't have to worry about the "pay 4 life" clause on Library at all right?
Pretty much. If you replace ALL of the draws, then you have no cards in hand that you've drawn that turn, so no cards to pay 4 life to keep. If you've drawn any other cards before that that turn, though, you'll still have to choose for them.
Relevant Gatherer Ruling:
9/16/2007: If you choose to draw two cards, then replace one or more of those draws with some other effect, the rest of Sylvan Library's ability still happens. If you've actually drawn only one card that turn, you must choose that card and either pay 4 life or put it on top of your library. If you haven't actually drawn any cards that turn, the rest of the ability has no effect.
Neato. Seems like a potent combination.